TEMPERATURE-INDUCED DEATH AND LYSIS IN A PSYCHROPHILIC BACTERIUM

Abstract

A Gram-negative rod isolated from flounder eggs grows in the temperature range 0–19 °C. At 21 °C there is no growth and at higher temperatures death occurs rapidly in, both seawater and seawater growth medium. After death, the cells lyse, as shown by decreased turbidity and the release of ultraviolet-absorbing substances. Lysis of non-growing cultures initiated at 25 °C can be retarded but not halted by lowering the temperature to 5 °C or 15 °C, temperatures at which cells not previously exposed to 25 °C remain viable and do not lyse. Lysis was not inhibited by a number of metabolic inhibitors, or by spermine. A small percentage of the total hexosamine is released by lysing cells, but the greatest change noted was the disappearance of most of the lipid phosphorus, probably representing the lipids of the cytoplasmic membrane. The breakdown of phosphatidyl ethanolamine, the major phospholipid in the cells, was demonstrated. Isolated cell envelopes also lyse at 25 °C, losing lipid phosphorus in the process. No evidence was found for a soluble lytic enzyme.